Field of the Invention
The present invention relates to an optical element such as a lens and a method for producing an optical element.
Description of the Related Art
Optical elements such as optical lenses have a nontransparent film (a light-shielding film) on their outer portion to prevent flares and ghosts. Optical elements such as optical lenses also have an antireflection film to reduce surface reflection and remove scattered light resulting from reflection.
Japanese Patent Laid-Open Nos. 2011-145627 and 2013-24922 disclose optical elements. These optical elements, an example being an optical lens, have a light-shielding film on their outer portion, a protective coating on the light-shielding film, and an antireflection film.
Japanese Patent Laid-Open No. 2010-54827 discloses a protective coating. This protective coating contains at least one of the following resins: epoxy, acrylic, imide, melamine, phenolic, novolac, alkyd, maleic acid, and silicone resins. According to the disclosure, this protective coating prevents dyes in a light-shielding film, such as a black dye, from dissolving out of the film.
The inventors found the optical elements disclosed in these publications to be disadvantageous in that when they are used for a long period of time under high-temperature and high-humidity conditions, the light-shielding film changes its shade of color and develops white spots. This disadvantage can be significant particularly if the optical element is washed with an alkaline aqueous solution after the attachment of the light-shielding film and the protective coating.
The present invention provides an optical element that maintains good appearance even through a long period of use under high-temperature and high-humidity conditions despite washing with an alkaline aqueous solution prior to the formation of an antireflection film.